This invention relates to a pressure-regulating device which is intended, for example, to equip the second stage of reduction of a two-stage pressure regulator of an air breathing apparatus, particularly an underwater breathing apparatus.
In the conventional air pressure-regulating devices for the second stage of reduction of an air breathing apparatus, the valve member of the second-stage valve is also urged constantly by a calibrated spring with a considerable force against its valve seat. This valve-closing force is also present when the valve is in its rest condition, and in the course of time this causes a permanent distortion of the resilient seal on the valve member, which alters the calibration of valve.
Inasmuch as the rest periods of this device are by far much longer than the periods of actual operation, it has been proposed, for example, as described in U.S. Pat. No. 4,094,314, to avoid any contact between the valve member and valve seat in the second-stage valves during the non-operative periods of the valves, by mounting the valve seat on a freely-floating member or piston, whereby the valve seat is matched against the valve member only when compressed air is operative upstream of the valve seat, whereas when the supply of compressed air is discontinued the piston is pushed back into a neutral position due to the resiliency of the seal on the valve member.
The device according to said U.S. Pat. No. 4,094,314 however, has some disadvantages and does not always result in a constant and reliable operation. Moreover, the force which matches the valve member against its seat cannot be adjusted.
Furthermore, all the conventional regulators mentioned above have the serious disadvantage of requiring the user, during the process of supplying air to him, to make an inhaling effort growing progressively with his air requirements. Accordingly, considerable breathing difficulties are often encountered by a user who, for example, is temporarily in a panting or gasping condition, i.e. is struggling for breath. The breathing functions of this user, in fact, are not facilitated by the conventional regulators.